Plasma generating apparatus and plasma processing apparatus

ABSTRACT

Provided is a microwave plasma generating apparatus using a multiple open-ended cavity resonator, and a plasma processing apparatus including the microwave plasma generating apparatus. The plasma processing apparatus includes a container for forming a process chamber, a support unit that supports a material to be processed in the process chamber, a dielectric window formed on an upper part of the process chamber, a gas supply unit that inject a process gas into the process chamber, and a microwave supply unit that includes a plurality of resonators for supplying microwaves through the dielectric window.

BACKGROUND OF THE INVENTION

This application claims the priority of Korean Patent Application No.2004-8174, filed on Feb. 7, 2004, in the Korean Intellectual PropertyOffice, the disclosure of which is incorporated herein in its entiretyby reference.

1. Field of the Invention

The present invention relates to a semiconductor apparatus, and moreparticularly, to an apparatus for generating microwave plasma using amultiple open-ended cavity resonator and a plasma processing apparatususing the multiple open-ended cavity resonator.

2. Description of the Related Art

Plasma is ionized gas with no macroscopic electric charge due to anequal presence of positively charged ions and negatively chargedelectrons. Plasma is generated at a very high temperature and in astrong electric field or an RF electromagnetic field.

Plasma is generated by glow discharge when free electrons excited by adirect current (DC) or an RF electric field collide with gas moleculesand generate active species such as ions, radicals, or electrons.Conventionally, a plasma process involves changing the characteristicsof a material surface by physical and/or chemical interaction betweenthe material surface and an obtained active species.

Currently, large area wafers are processed in the mass production ofsemiconductor devices. In order to perform a plasma process on alarge-area wafer, a plasma processing apparatus must be able toaccommodate the large-area wafer and generate plasma having uniformdensity. Such an apparatus is becoming increasingly important insemiconductor device production.

Among plasma generating apparatuses, research into plasma processingapparatuses using microwaves is currently in progress.

FIG. 1 is a cross-sectional view of a conventional plasma processingapparatus 10 using a bidirectional distributor.

The plasma processing apparatus 10 depicted in FIG. 1 is disclosed inU.S. Pat. No. 6,497,783, dated Dec. 24, 2002, and entitled “PLASMAPROCESSING APPARATUS PROVIDED WITH MICROWAVE APPLICATOR HAVING ANNUNLARWAVEGUIDE AND PROCESSING METHOD”. The plasma processing apparatus 10includes a container 11 for forming a processing chamber 19, a holdingunit 12 that supports a wafer W loaded in the processing chamber 19, aheater 25 coupled under the holding unit 12, a gas supply unit 17 havinga gas supply port 17 a, a dielectric window 14 mounted on an upper partof the processing chamber 19 that isolates the processing chamber 19from the outside atmosphere, and a microwave supply unit 13 formed onthe dielectric window 14.

FIG. 2 is a perspective view of the microwave supply unit 13 of theconventional plasma processing apparatus 10 shown in FIG. 1.

Referring to FIGS. 1 and 2, the microwave supply unit 13 is a resonatorformed of a conductive material, includes a space 13 a through whichmicrowaves propagate, upper and lower walls 13 c and 13 g, a pluralityof slots 13 b formed in the lower wall 13 c adjacent to the dielectricwindow 14, a side wall 13 d, a microwave introducing port 13 e formed onthe upper surface 13 g, and a distributor 13 f for introducingmicrowaves supplied from a waveguide 15 to the space 13 a by dividinginto two parts.

Referring to FIG. 1, the conventional plasma processing apparatus 10includes a microwave power source 6 having a microwave oscillator suchas a magnetron, at least two gas supply units, and a gas exhaust system.Each of the gas supply units includes a gas source 21, a valve 22, and amass flow controller (MFC) 23. The gas exhaust system includes anexhaust control valve 26, a cut-off valve 25 a, and a vacuum pump 24.

Plasma generation and processing in a conventional plasma processingapparatus 10 is performed as follows.

A wafer W is loaded onto a holding unit 12 and heated to a desiredtemperature. The processing chamber 19 is evacuated by the vacuum pump24 and a plasma process gas flows into the process chamber 19 at aconstant flow rate from the gas supply unit 17.

Next, power is applied to the microwave supply unit 13 from themicrowave power source 6 via the waveguide 15. Microwaves supplied fromthe microwave supply unit 13 propagate into space 13 a after beingdivided into two parts by the distributor 13 f. The divided microwavesform standing waves by interfering with each other in space 13 a.

The microwaves are strengthened at the plurality of slots 13 b, andpropagate into the process chamber 19 via the plurality of slots 13 band the dielectric window 14. An electric field of the microwavessupplied to the process chamber 19 accelerates electrons to generatehigh-density plasma at an upper part of the plasma process chamber 19.The processing gas in the process chamber 19 is then excited by the highdensity plasma to process a surface of the wafer W loaded on the holdingunit 12.

FIGS. 3 a and 3 b show a pattern of plasma formed by microwaves radiatedfrom the plurality of slots 13 b of the microwave supply unit 13, and apattern of erosion corresponding to the slots 13 b, respectively, whenperforming a deposition process using the conventional plasma processingapparatus 10.

Referring to FIGS. 3 a and 3 b, the conventional plasma processingapparatus 10 has an additional device having a plurality of slots Abetween a lower part of the microwave supply unit 13 and the dielectricwindow 14 to improve the density uniformity of plasma B. However, theadditional device having the plurality of slots A causes erosion of thedielectric window 14 and consequent generation of unwanted particles.When performing a deposition of etching process using the conventionalplasma processing apparatus, these unwanted particles, originating fromerosion of the dielectric window 14, become impurities in a deposited oretched thin film.

SUMMARY OF THE INVENTION

The present invention provides a microwave plasma generating apparatusthat can form a high-density and uniform plasma source in the vicinityof a material to be processed, and a plasma processing apparatus.

The present invention also provides a microwave plasma generatingapparatus that can minimize power loss and avoid erosion of a dielectricwindow, and a plasma processing apparatus.

According to an aspect of the present invention, there is provided aplasma processing apparatus comprising a container for forming a processchamber, a support unit that supports a material to be processed in theprocess chamber, a dielectric window formed on an upper part of theprocess chamber, a gas supply unit that inject a process gas into theprocess chamber, and a microwave supply unit that includes a pluralityof open ended cavity resonators for supplying microwaves through thedielectric window.

According to another aspect of the present invention, there is provideda microwave supply unit comprising a microwave power source forgenerating microwaves, a plurality of waveguides, a coupler fordistributing the microwaves generated by the microwave power source tothe plurality of waveguides, and a plurality of open ended cavityresonators.

According to another aspect of the present invention, when processing amaterial in a process chamber using a plasma processing apparatus havinga microwave supply unit that includes a process chamber and a pluralityof open-ended cavity resonators, uniform plasma density over thematerial can be maintained by individually controlling power supplied tothe plurality of open-ended cavity resonators.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present inventionwill become more apparent by describing in detail exemplary embodimentsthereof with reference to the attached drawings in which:

FIG. 1 is a cross-sectional view illustrating a conventional plasmaprocessing apparatus;

FIG. 2 is a perspective view of a microwave supply unit of theconventional plasma processing apparatus shown in FIG. 1;

FIGS. 3 a and 3 b show a pattern of plasma formed by microwaves radiatedfrom a plurality of slots of the microwave supply unit, and a pattern oferosion corresponding to the slots, respectively, when performing adeposition process using the conventional plasma processing apparatusshown in FIG. 1;

FIG. 4 is a cut-away perspective view of a plasma processing apparatusaccording to an embodiment of the present invention;

FIG. 5 is a cross-sectional view of a microwave supply unit of theplasma processing apparatus of FIG. 4;

FIG. 6 is a graph of plasma density versus distance from a dielectricplate of the plasma processing apparatus of FIG. 4;

FIG. 7 is a schematic drawing illustrating a standing wave formed by asingle resonator in a process chamber of the plasma processing apparatusof FIG. 4; and

FIG. 8 is a graph illustrating plasma density peaks generated by each ofa plurality of resonators in the process chamber of the plasmaprocessing apparatus of FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described more fully with reference tothe accompanying drawings in which a preferred embodiment of theinvention is shown. Like reference numerals refer to like elementsthroughout the drawings.

FIG. 4 is a cut-away perspective view illustrating a plasma processingapparatus according to an embodiment of the present invention.

As depicted in FIG. 4, a plasma processing apparatus 100 according to anembodiment of the present invention comprises a container 111 forforming a process chamber 109, a support unit 102 for supporting asubstrate such as a wafer in the process chamber 109, a first gas supplyunit 107 that includes a first gas inlet port 107 a, a second gas supplyunit 117 that includes a second gas inlet port 117 a, a dielectricwindow 104 combined with an upper part of the process chamber 109 thatseparates the process chamber 109 from the outer atmosphere, and amicrowave supply unit 130 formed on the dielectric window 104.

FIG. 5 is a cross-sectional view of the microwave supply unit 130 of theplasma processing apparatus 100 of FIG. 4.

The microwave supply unit 130 comprises a microwave power source 132, acoupler 134, an upper gas supply unit 108 that includes an upper gasinlet port 108 a, a cooling water inlet port 136 a, a cooling wateroutlet port 136 b, first through n^(th) waveguides 103 ₁ through 103_(n), and first through n^(th) resonators 113 ₁ through 113 _(n).

The microwave power source 132 of the microwave supply unit 130 includesa microwave generator such as a magnetron. The microwaves generated bythe microwave power source 132 are supplied to the first through n^(th)resonators 113 ₁ through 113 _(n) through each of the first throughn^(th) waveguides 103 ₁ through 103 _(n) by the coupler 134.

The first through n^(th) resonators 113 ₁ through 113 _(n) according tothe present invention, as parts of a multiple open-ended cavityresonator, have open-ends where they connect to the first through n^(th)waveguides 103 ₁ through 103 _(n) and the dielectric window 104.Therefore, plasma distribution in the process chamber 109 can be madeuniform by uniformly distributing microwaves over the entire surface ofthe dielectric window 104.

Referring to FIG. 4, in the plasma processing apparatus 100 according toan embodiment of the present invention, the upper gas supply unit 108performs two functions. The first function is supplying cleaning gas forcleaning the process chamber 109 after depositing or etching a thin filmon a substrate loaded on the support unit 102. For example, C₂F₆ gas maybe supplied for cleaning the process chamber 109 after depositing a SiO₂thin film. The other function is mechanically supporting a centerportion of the dielectric window 104.

By mechanically supporting the center portion of the dielectric window104, a large and relatively thin dielectric window 104 can be supportedwith reduced mechanical stress.

For uniform distribution of a process gas supplied to the substrate, aplasma source housing 107 f includes the first gas supply unit 107 thatincludes the first gas inlet port 107 a for injecting the process gas ata predetermined angle to a surface of the substrate. The second gassupply unit 117 including the second gas inlet port 117 a is locatedunder the plasma source housing 107 f and is structured to provide auniform distribution of gas flux in all azimuthally. Gas flux througheach of the gas inlet ports described above can be controlledindependently. Therefore, the distribution of the process gas suppliedto the substrate can be made uniform.

A direct cooling system for cooling the dielectric window 104 isemployed. That is, cooling water entering through the cooling waterinlet port 136 a directly contacts the dielectric window 104 and isdischarged through the cooling water outlet port 136 b to the outsideafter reducing a temperature gradient in the radial direction of thedielectric window 104.

The plasma processing apparatus 100 depicted in FIG. 4 uses a pair ofco-axial type resonators, i.e., first and second resonators 113 ₁ and113 ₂, for exciting the microwave plasma in the process chamber 109. Thesecond resonator 113 ₂ is located near an edge of the dielectric window104. The second resonator 113 ₂ is a bottom open-ended cavity resonator,and functions to generate very high-density plasma near the edge of theprocess chamber 109.

The microwave power generated by the microwave power source 132 entersthe first and second waveguides 103 ₁ and 103 ₂ through the coupler 134.Each of the microwaves entering the first and second waveguides 103 ₁and 103 ₂ enters each of the first and second resonators 113 ₁ and 113 ₂via tapered waveguide units 105 ₁ and 105 ₂ connected to each of thewaveguides 103 ₁ and 103 ₂.

An amount of microwave power generated by the microwave power source 132and entering into the first and second resonators 113 ₁ and 113 ₂ can becontrolled by first and second combining probes 112 a and 112 b includedin the first and second waveguides 103 ₁ and 103 ₂.

Controlling the microwave entering into the first resonator 113 ₁ cancontrol density of microwave plasma at the center portion of the processchamber 109. For example, changing a ratio of microwave powertransmitted to the second waveguide 103 ₂ can control plasma uniformityin the radial direction in the process chamber 109.

The plasma processing apparatus 100 depicted in FIG. 4 uses a microwaveplasma generating device composed of the first and second resonators 113₁ and 113 ₂. However, a plasma processing apparatus according toalternative embodiments of the present invention may use a microwaveplasma generating device composed of any number of resonators.

In the case of a plasma processing apparatus according to an alternativeembodiment of the present invention that uses a microwave plasmagenerating device employing n resonators, plasma uniformity in thevicinity of the dielectric window 104 in the process chamber 109 can becontrolled by controlling a ratio of microwave power entering each ofthe resonators by controlling the coupler 134.

Also, although not shown, employing an individual microwave power sourcein each of the waveguides can control plasma uniformity.

The first and second movable flanges 115 a and 115 b are used formatching each of the waveguides to the corresponding microwave powersources.

Also, the first waveguide 103 ₁ can be rotated with respect to an axisof the process chamber 109, and the second waveguide 103 ₂ can bestructured to rotate with respect to the first waveguide 113 ₁.Accordingly, the microwave plasma generating device can be easilycombined with the plasma processing apparatus.

The support unit 102 is located under the process chamber 109 and canmove up and down to place the substrate loaded on the support unit 102at a level at which plasma uniformity is optimum.

According to the present invention, the plurality of microwavewaveguides is co-axial and adjacent microwave waveguides share a wall.

FIG. 6 is a graph of plasma density versus distance from the dielectricwindow 104 toward a wafer substrate W mounted on the support unit 102 ofthe plasma processing apparatus of FIG. 4.

Referring to FIG. 6, d₂ represents optimum uniformity of plasma in theradial direction of the substrate W, and d₁ and d₃ represent lessfavorable plasma distributions. Since the wafer substrate W can belocated at an optimum distribution region of plasma by adjusting adistance between the dielectric window 104 and the wafer substrate W, itis not necessary to create uniform plasma in the whole volume of processchamber 109 in order to get uniform flux on the substrate W. It issufficient to control the individual plasma density peaks generated bythe plurality of resonators 113 ₁ through 113 _(n) in the processchamber 109.

FIG. 7 is a schematic drawing illustrating a standing wave formed by asingle resonator in the process chamber 109.

Referring to FIG. 7, a standing wave has a peak at a locationcorresponding to a center line off the resonator. The amplitude of thestanding wave indicates the magnitude of microwave power, and the plasmadensity in the process chamber 109 varies according to the microwavepower.

FIG. 8 is a graph illustrating plasma density peaks generated by each ofthe plurality of resonators 113 ₁ through 113 _(n) in the processchamber 109. For simplicity, the cooling water inlet port 136 a and thecooling water outlet port 136 b are omitted.

Referring to FIG. 8, a center peak 0 at the center of the processchamber 109 is formed by the first resonator 113 ₁. Peaks 0 ₂ through 0_(n) are formed at locations corresponding to center lines of the secondthrough the nth resonators 113 ₂ through 113 _(n). Since all of theresonators are symmetrical with respect to the center of the processchamber 109, the peaks also have azimuthal symmetry. Accordingly, a topview of the peaks is a concentric circle.

The resonators are arranged to form the peaks 0 ₂-0 _(n) at apredetermined distance from the center peak 0. Thus, as described above,the plasma density is varied according to distance from the dielectricwindow 104 in the process chamber 109, as depicted in FIG. 6. Therefore,according to the present invention, uniform plasma density in the radialdirection at a predetermined distance from the dielectric window 104 canbe obtained even if the plasma density is not uniform throughout theentire process chamber 109.

In order to form peaks at locations corresponding to the center lines ofthe resonators, resonance must occur in each of the resonators. Aresonance condition of each of the resonators according to the presentinvention is that the perimeter of resonator center line must be equalto integer number of wavelengths of the microwave for waveguidecorresponding to the resonator. At this time, it should be noted that,in the case of an open-type waveguide, the wavelength is not the same asin the case of a closed-type waveguide with conductive walls on allsides. This is because, in the open-type waveguide, not only a bentupper ring constituting the waveguide but also the dielectric window andthe process chamber together form a resonator.

Even though an oscillation frequency in the resonator is determined bythe frequency input from the microwave supply unit, the types of modeexcited in each resonator also depend on location of coupling device. Asfar as the coupling occurs through a number of independent ports, eachof input microwaves will excite its own resonance mode at samefrequency.

Changing a ratio of microwave power transmitted to the correspondingresonator can control the amplitude of a peak at a given radialposition. As depicted in FIG. 5, the microwave supply unit according tothe present invention enables the use of three or more co-axialresonators at different radial distances from the center, and this isimportant for enabling uniform plasma processing over a large region.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those of ordinary skill in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the present invention as defined by the following claims.

As described above, due to the structure of the plasma processingapparatus according to the present invention, plasma can be formed witha uniform distribution over a large substrate using a plurality ofring-type open-ended cavity resonators.

Also, erosion of a dielectric window can be avoided since the plasmaprocessing apparatus according to the present invention does not use aplurality of slots for supplying microwaves through the dielectricwindow.

Also, a process gas can be ionized and decomposed effectively bysupplying the process gas to locations close to the dielectric window.

1. A plasma processing apparatus comprising: a container for forming aprocess chamber; a support unit that supports a material to be processedin the process chamber; a dielectric window formed on an upper part ofthe process chamber; a gas supply unit that inject a process gas intothe process chamber; and a microwave supply unit that includes aplurality of open ended cavity resonators for supplying microwavesthrough the dielectric window.
 2. The plasma processing apparatus ofclaim 1, wherein the gas supply unit comprises: an upper gas supply unitmounted through the center of the dielectric window; a first gas supplyunit for supplying the process gas to a surface of the material to beprocessed at a predetermined angle; and a second gas supply unitconfigured to have a radially uniform distribution of gas flux.
 3. Theplasma processing apparatus of claim 2, wherein gas flux through each ofthe gas supply units is independently controlled.
 4. The plasmaprocessing apparatus of claim 1, wherein the plurality of open-endedcavity resonators are open at portions contacting the dielectric window.5. The plasma processing apparatus of claim 1, wherein the microwavesupply unit comprises: a microwave power source for generatingmicrowaves; a plurality of waveguides; a coupler for distributing themicrowaves generated by the microwave power source to the plurality ofwaveguides; and a plurality of open ended cavity resonators connected toa plurality of waveguides, respectively.
 6. The plasma processingapparatus of claim 5, wherein radial plasma uniformity in the processchamber can be improved by changing a ratio of microwave powertransmitted to each of the waveguides.
 7. The plasma processingapparatus of claim 5, wherein each of the waveguides are capable ofrotation with respect to an axis of the process chamber.
 8. The plasmaprocessing apparatus of claim 5, wherein the plurality of waveguides areconfigured to be co-axial.
 9. The plasma processing apparatus of claim5, wherein adjacent waveguides share a common wall.
 10. The plasmaprocessing apparatus of claim 1, wherein the supporting means is able tomove up and down to locate a substrate loaded on the supporting means ata level of optimum plasma uniformity.
 11. A microwave supply unitcomprising: a microwave power source for generating microwaves; aplurality of waveguides; a coupler for distributing the microwavesgenerated by the microwave power source to the plurality of waveguides;and a plurality of resonators.
 12. The microwave supply unit of claim11, wherein the coupler adjusts a ratio of microwave power transmittedto each of the waveguides.
 13. The microwave supply unit of claim 11,wherein the waveguides are capable of rotation with respect to eachother.
 14. The microwave supply unit of claim 11, wherein portions ofthe plurality of open-ended cavity resonators opposite to the waveguidesare open.
 15. The microwave supply unit of claim 11, wherein theplurality of waveguides are configured co-axially.
 16. The microwavesupply unit of claim 11, wherein adjacent waveguides share a commonwall.